U.S. patent number 7,742,176 [Application Number 10/595,185] was granted by the patent office on 2010-06-22 for method and system for determining the spatial position of a hand-held measuring appliance.
This patent grant is currently assigned to Leica Geosystems AG. Invention is credited to Beat Aebischer, Bernhard Braunecker, Bernhard Gachter.
United States Patent |
7,742,176 |
Braunecker , et al. |
June 22, 2010 |
Method and system for determining the spatial position of a
hand-held measuring appliance
Abstract
The aim of the invention is to determine the actual position
and/or actual orientation of a measuring appliance (4b). To this
end, at least two reference points (2b') lying in a spatial segment
(5') scanned by a laser beam are detected and measured in terms of
the distance thereinbetween and the inclination angle thereof. The
actual position of the measuring appliance (4b) can be deduced from
the known positions of said reference points (2b') arranged in a
detectable manner and the associated distances and inclination
angle thereof. The detection, monitoring and measuring of the
reference points is carried out by the measuring appliance (4b) in
an automated manner, the measuring appliance (4b) and specifically
embodied elements associated with the reference points (2b')
forming a local positioning and/or orientation measuring system.
The inventive method and corresponding devices enable measurements
to be carried out in a problem-free and automated manner, even in
areas that cannot be accessed by other measuring systems.
Inventors: |
Braunecker; Bernhard (Rebstein,
CH), Gachter; Bernhard (Balgach, CH),
Aebischer; Beat (Heerbrugg, CH) |
Assignee: |
Leica Geosystems AG (Heerbrugg,
CH)
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Family
ID: |
34178437 |
Appl.
No.: |
10/595,185 |
Filed: |
September 21, 2004 |
PCT
Filed: |
September 21, 2004 |
PCT No.: |
PCT/EP2004/010571 |
371(c)(1),(2),(4) Date: |
July 17, 2006 |
PCT
Pub. No.: |
WO2005/031259 |
PCT
Pub. Date: |
April 07, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070064246 A1 |
Mar 22, 2007 |
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Foreign Application Priority Data
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Sep 22, 2003 [EP] |
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03021134 |
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Current U.S.
Class: |
356/614; 356/3;
356/622; 356/140 |
Current CPC
Class: |
G01S
17/06 (20130101); G01C 15/002 (20130101) |
Current International
Class: |
G01B
11/14 (20060101) |
Field of
Search: |
;356/3-5.09,614,622,623,139.1,140 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0341890 |
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Nov 1989 |
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EP |
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0468677 |
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Jan 1992 |
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EP |
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1424156 |
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Feb 2004 |
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EP |
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1424884 |
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Feb 2004 |
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EP |
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WO82/01420 |
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Apr 1982 |
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WO |
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Primary Examiner: Toatley, Jr.; Gregory J
Assistant Examiner: Alli; Iyabo S
Attorney, Agent or Firm: Workman Nydegger
Claims
The invention claimed is:
1. A method for determining a spatial position of a hand-held
measuring appliance, wherein a quantity of reference points have
been made detectable, the quantity of reference points comprising
at least two reference points, and wherein the hand-held measuring
appliance is configured to detect and measure the reference points
by means of laser radiation, the method comprising the following
acts: deriving positions of the reference points by surveying the
reference points from at least one known initial position;
automatically detecting and deriving location information relative
to at least one first and one second reference point from the
quantity of reference points using the measuring appliance, wherein
at least one spatial segment is automatically scanned in a scanning
movement by the laser radiation to detect the first and second
reference points; and wherein the location information for at least
the detected first and second reference points is derived by
measuring at least: the distance between the measuring appliance
and the first reference point; and the distance between the
measuring appliance and the second reference point and/or the angle
(.gamma.) between the first and second reference points; and the
angle of inclination (.alpha., .beta.) to the first or to the
second reference point; or at least one distance to a third
reference point; and deriving an actual position of the measuring
appliance from the location information and the positions of at
least the first and second reference point.
2. The method of claim 1, further comprising repeating at least one
of the acts of claim 1.
3. A method according to claim 1, wherein in the automatic
detection and derivation of location information: at least an
inclination of the measuring appliance is derived; an emission
direction of the laser radiation is determined indirectly or
directly; and/or an actual orientation of the measuring appliance
is derived.
4. A method according to claim 3, wherein the emission direction is
determined by configuring a defined trajectory.
5. A method according to claim 1, wherein the first and second
reference points are detected on the basis of their reflectivity of
the laser radiation.
6. A method according to claim 5, wherein the first and second
reference points are detected on the basis of their reflectivity of
the laser radiation by using cooperative targets for establishing
the reference points.
7. A method according to claim 1, wherein the automatic detection
includes distinguishing the reference points from one another by
recognition of individual codes or individual physical properties
coordinated with each reference point.
8. A method according to claim 7, wherein the points are
distinguished on the basis of spectral selectivity.
9. A method according to claim 1, wherein the act of automatic
detection and derivation of location information includes recording
of images.
10. A method according to claim 9, wherein the first and/or second
reference points are detected using image processing methods.
11. A method according to claim 9, wherein the location information
for at least the detected first and second reference points is
derived using image processing methods.
12. A method according to claim 1, wherein the scanning movement is
effected in a substantially rosette or zig zag manner.
13. A method according to claim 1, wherein the act of automatic
detection includes automatic target tracking of at least one of the
reference points.
14. A method according to claim 1, wherein the location information
and/or the alignment information for at least the detected first
and second reference points are simultaneously derived.
15. A method according to claim 1, further comprising the act of
deriving the actual position and/or an actual orientation by means
of inertial sensors.
16. A method according to claim 15, wherein the act of deriving the
actual position and/or actual orientation by means of inertial
sensors includes interpolation of the actual position and/or of the
actual orientation.
17. A method according to claim 1, wherein at least one of the
distances is measured according to one of the following principles:
phase measurement; pulse transit time measurement; pulse transit
time measurement with threshold value determination; or pulse
transit time measurement with HF sampling.
18. A method according to claim 1, further comprising the act of
correcting deviations of a positioning and/or orientation measuring
device based on inertial sensors.
19. A method according to claim 18, wherein the deviations include
drift effects.
20. A method according to claim 1, further comprising: marking
processing positions; defining a first actual position as a start
position; defining a second actual position as an end position,
wherein processing positions are automatically derived according to
a specified scheme between start position and end position.
21. A method according to claim 20, further comprising verifying a
processing position by performing the method of claim 1.
22. A measuring appliance configured to perform the method of claim
1.
23. A measuring appliance comprising: a laser radiation source for
producing laser radiation; a measuring component configured to
automatically detect reference points which have been made
detectable, the measuring component further configured to derive
location information of the reference points, the measuring
component comprising a receiver configured to receive the laser
radiation, the receiver being configured to measure distance; a
control component configured to change the emission direction of
the laser radiation, the control component being configured so that
at least one spatial segment is automatically scanned by laser
radiation; and a position component configured to derive the actual
position of the measuring appliance from the location information
of the reference points, wherein the measuring appliance is sized
and configured to be hand-held.
24. A measuring appliance according to claim 23, wherein the
measuring component is further configured to derive the positions
of the reference points.
25. A measuring appliance according to claim 23, wherein the
measuring component is configured to measure angles.
26. A measuring appliance according to claim 25, wherein the
measured angles are between two reference points, between a
reference point and the horizontal, and/or between the measuring
appliance and the horizontal.
27. A measuring appliance according to claim 23, wherein the
measuring component is configured to determine the emission
direction of the laser radiation relative to an axis of the
measuring appliance.
28. A measuring appliance according to claim 23, further comprising
inertial sensors.
29. A measuring appliance according to claim 23, wherein the
control component includes a scanner.
30. A measuring appliance according to claim 29, wherein the
scanner includes at least one rotatable prism or mirror.
31. A measuring appliance according to claim 23, wherein the
measuring component includes an image-recording component.
32. A measuring appliance according to claim 31, wherein the
image-recording component includes a CCD or CMOS camera.
33. A measuring appliance according to claim 31, wherein the
image-recording component includes a wide-angled camera.
34. A measuring appliance according to claim 23, wherein the
measuring component includes a scanning detection component.
35. A measuring appliance according to claim 34, wherein the
scanning detection component includes a coaxial optical system.
36. A measuring appliance according to claim 34, wherein the
scanning detection component includes an endoscope.
37. A measuring appliance according to claim 23, further comprising
a telemeter.
38. A measuring appliance according to claim 23 wherein the control
component is configured to vary the extent of the spatial
segment.
39. A measuring appliance according to claim 23, wherein the
control component is configured to scan at least two spatial
segments independently of one another.
40. A measuring appliance according to claim 39, wherein the
control component includes two trackers for target tracking.
41. A measuring appliance according to claim 23, further comprising
a display for confirming that the measuring appliance has assumed a
predetermined position.
42. A measuring appliance according to claim 41, further comprising
a computing component configured to derive predetermined
positions.
43. A measuring appliance according to claim 42, wherein the
computer component derives the predetermined positions by
establishing a start position and an end position between which
processing positions are automatically derived by the computing
component according to a specified scheme.
44. A local position-determining system comprising a measuring
appliance according to claim 23, the local position-determining
system further comprising at least two reflectors for establishing
reference points which have been made detectable.
45. A local position-determining system according to claim 44,
wherein at least one of the reflectors includes one of the
following elements: a glass sphere, in particular as full spheres
or hemispheres, a retroreflective foil, or a triple prism.
46. A local position-determining system according to claim 45
wherein at least one of the reflectors is an element provided with
a coding or a spectral selectability.
Description
The invention relates to a method for determining the spatial
position of a hand-held measuring appliance according to claim 1, a
use of the method for correcting deviations of a positioning and
orientation-measuring device based on inertial sensors, according
to claim 14, a hand-held measuring appliance according to the
precharacterizing clause of claim 15, a local position
determination system according to claim 27 and a use of the method
according to claim 29.
In many geodetic applications, methods and systems for position
and/or orientation determination of a geodetic instrument are used.
From a position determined by such a system, further measurements
which are linked to the position and generally also require a
knowledge of the spatial orientation of the measuring appliance are
generally then carried out. For such applications, the 6 degrees of
freedom of the hand-held measuring appliance have to be determined
for unambiguously establishing the absolute spatial position. The
problem thus comprises the determination of position and
orientation as two fundamentally separately achievable tasks,
which, however, have to be carried out in association for many
applications. As a rule, both position and orientation of a
hand-held measuring appliance are therefore required.
An example of systems for position determination are global
positioning systems, such as, for example, GPS, GLONASS or the
European Galileo system currently being established. These systems
are based on the as far as possible undisturbed reception of
satellite signals, which, however, may also be obstructed by
obstacles and thus limited in their usability. In the immediate
vicinity of obstacles, the reception of the signals may be limited
or completely impossible owing to the obstructive effect of said
obstacles, so that position determination using this system is no
longer possible. These limitations relate in particular to
measurements in interior rooms of buildings in which the reception
of a number of satellites which is required for positioning can
generally be ruled out. A further problem is that global
positioning systems do not always provide the required accuracy of
position determination or require a greater effort, for example by
use of a reference station or longer measuring times.
The determination of the orientation of a measuring appliance using
such systems is possible, for example, by the use of two receiving
aerials. If the position of the baseline or of the aerials relative
to the axis of the appliance is known, it is possible to conclude
the orientation of the measuring appliance. In order to determine
thereby the still undetermined rotation about the axis of the
appliance, an inclination sensor can be used.
A further example is the position determination of a
reflector-bearing instrument using a theodolite or tacheometer. By
a direction and distance measurement with the tacheometer to the
geodetic instrument, the position of the instrument too can be
determined if the position of the tacheometer is known. In
combination with automated target detection and target tracking, a
quasi-continuous position determination can be achieved. A
precondition for the measurement here is the visual link between
the two components. If this link is interrupted, for example by
growth or buildings in the field of view, the method of position
determination fails. Furthermore, only one instrument at a time can
be tracked by a motorised tacheometer, so that, for example in the
case of many vehicles on a building site, a large number of
theodolites also have to be used. The use of a large number of
theodolites which cover virtually the entire area to be surveyed
without gaps in the visible area is generally impractical owing to
the cost in terms of equipment and personnel. Moreover, such a
solution results in high complexity and demands constant
communication for controlling the measuring process.
In order to permit the actual position as the current location of
the instrument under all conditions with the required accuracy,
methods are known which are based on a determination of the
position of said instrument itself relative to objects known with
regard to their position, as reference objects or reference points.
An example of this is the classical method of trilinear surveying.
If it is intended to derive actual positions for a geodetic
instrument or a positioning device suitable for this purpose from a
knowledge of reference points, the reference points must be
established beforehand and surveyed with sufficient accuracy.
The determination of the actual position is subsequently effected
by a measurement to the reference points, from which conclusions
can be drawn about the location of the instrument itself or the
actual position. In many cases, a geodetic instrument has only an
ability for distance measurement, or a measurement of angles cannot
be carried out with the required precision or speed. In these
cases, the position determination must be carried out by distance
measurements alone. For this purpose, the distances to a plurality
of points of known position are measured, and the determination of
the actual position can be effected by known methods as also used,
for example, in photogrammetry. Correlation methods or correlation
calculations are an example of this. The number of points required
is dependent on the position thereof and the intended accuracy of
the measurement. As a rule, however, apart from particularly
favourable configurations, at least 3 or 4 points are required. If
in addition an angle is to be taken into account, for example by
additionally detecting the angle relative to the horizontal, the
number of points can be reduced to two.
The number of points actually required in each case is dependent on
the position of the known points and any possible limitations for
reducing ambiguity. In the case of three distance measurements to
the various reference points, a plane at which the actual position
to be determined can be reflected is defined by the three known
positions. Two possible positions arise as a solution, of which,
however, one position is generally ruled out for plausibility
reasons, for example because it would lie below the surface of the
Earth, or on the basis of simple further information, such as, for
example, the distinction between North and South, which can also be
made by means of a simple magnetic compass. An unambiguous
determination with three known points is possible if favourable
geometric conditions are present. This is the case, for example, if
the position sought lies on a connecting line between two known
points.
Apart from the position, in principle the spatial orientation of a
structure may also be determined by means of geodetic devices, by
carrying out measurements from two or three points of the
structure, although only 5 degrees of freedom can be determined by
measurement from only two points. Owing to the spatial dimensions
of hand-held appliances, however, such an approach is not
practicable.
In spite of this fundamentally known possibility for determining an
actual position, the procedure using geodetic instruments of the
prior art is moreover prohibitively complicated and, owing to the
necessary measurements, always requires an interruption of the
activity otherwise taking place. In particular, it is not possible
to carry out measurements constantly out of a continuing movement
or even to use the determination of the actual position according
to this principle for correcting errors of positioning systems of
other types.
U.S. Pat. No. 5,467,273 discloses a robot system for movements in
an extensive plane, which system determines the position and
orientation of said system itself by reference to known, reflecting
points. For this purpose, the robot system uses a scanner system
movable about a vertical axis and having a telemeter which measures
distance and angle to the reference points and determines the
actual position therefrom.
Owing to the limitation of the movement in a plane, however, the
determination of location and direction is not very complex here
and cannot be directly applied to a three-dimensional problem.
Moreover the accuracies required for controlling a robot system of
this type are significantly lower than those of geodetic
applications.
Of particular relevance here is the number of reference points
required for a measurement with a specified accuracy. Said number
should be as low as possible, particularly during initial setup and
surveying of such points. In order to minimize the number of
reference points required, a careful choice of the setup geometry
and of the variables to be measured is therefore required.
An object of the present invention is to provide a method, an
apparatus and a system which permits the determination of the
actual position and of the orientation of a hand-held measuring
appliance even in highly transected terrain or in interior
rooms.
A further object is to shorten the periods between the necessary
measurements.
A further object is the provision of a local positioning and
orientation system in which the electronics required for
determining the spatial position can constantly be carried along
with the unit whose position is to be determined and which, in its
design, is therefore substantially independent of the number of
users.
The increase in the accuracy of determination of actual position
and actual orientation is a further object of the present
invention.
A further object is the simplification and shortening of the
measurements for determining actual position and actual
orientation.
A further object of the invention is to permit automatic
identification and surveying of the reference points.
A further object of the invention is to permit automatic
determination and checking of processing points between defined
start and end points.
A further object of the present invention is to provide a method, a
hand-held measuring appliance or a positioning and orientation
system which permits a continuous correction of the measurements of
positioning and orientation systems based on other principles of
operation, said correction preferably taking place in the
background.
These objects are achieved, according to the invention, by features
of claims 1, 14, 15, 27 and 29, respectively, or by features of the
subclaims.
The invention relates to a method and a positioning device or
system for determining the actual position, in particular in
association with the use of a geodetic instrument.
For this purpose, a number of reference points is established, made
detectable and surveyed in a first step of the method. This
quantity of reference points is chosen so that as far as possible
at least two of the reference points can be detected from each
point of the region to be used. Surveying of the positions of these
reference points can be effected using generally known methods of
surveying technology, for example by means of a total positioning
system or a global positioning system or by aerial photogrammetry.
If the reference points are present in closed rooms, they can also
be surveyed, for example, using hand-held telemeters, either the
distance to the same reference point being recorded from a
plurality of known positions or it being possible to use further
information, such as, for example, from angle measurements. In
principle an already measured trigonometrical point can also be
chosen as a reference point. The reference points can, however,
also be surveyed with the positioning device according to the
invention relative to a specified starting point on which the
positioning device is initially placed.
In order to make the reference points detectable, they are defined
by mounting specially designed elements. Cooperative targets, such
as, for example, triple prisms, reflective foils or other
reflectors customary in surveying technology can be used for this
purpose. The use of spherical elements provides a combination of
accurate determination of a reference point with good detectability
from different directions. Said elements may be, for example, in
the form of reflective spheres or in the form of hemispheres or
quarter-spheres. Because of the form and the reflectivity of the
surface, incident laser radiation is reflected back equally for all
directions of incidence. Owing to the fixed radius, the distance to
the defined point can be accurately calculated. Moreover, owing to
the centre of gravity of the reflection on the surface of the
sphere or of the sphere segment, the position of the reference
point can also be determined for angle measurements with sufficient
accuracy.
Particularly in association with a relatively long-term use of an
area, for example a large building site, it is possible, by setting
up a large number of reference points, to define a network of known
positions which can be seen from most areas and which represent the
basis of this local positioning system and, owing to the advantages
of a relatively long duration of use, can also be measured with
greater effort.
The positioning device according to the invention has at least one
radiation source for emission of laser radiation. After emission
and subsequent reflection at a surface, this laser radiation is
once again detected and evaluated in a receiver, a distance
measurement based on the phase measuring principle or the principle
of pulse transit time measurement being carried out. Such an
apparatus is disclosed, for example, in EP 0 738 899 B1. A further
principle for distance measurement which can be used according to
the invention is described in WO 2004/074773.
The laser beam is guided over at least one spatial segment in a
scanning movement, it being necessary for spatial segment, number
of reference points and orientation of the detected spatial segment
to be tailored to one another in such a way that, for the purpose
of a distance measurement, at least two of the reference points are
located in one spatial segment or in each case one reference point
is located in one of two spatial segments. Depending on the
specifically chosen realisation of an embodiment, different
scanning movements can be chosen for the spatial segment. Thus, for
example in the case of the use of counterrotating prisms as a
control element of a scanner, rosette-like scanning of a circular
scanned or detected spatial segment is possible.
The reference points can in principle be detected if the spatial
segment passes over a region and reference points entering the
spatial segment or present therein are detected, identified and
surveyed. In addition, with the use of components for independent
scanning of a plurality of spatial segments, it is also always
possible to track one or more reference points. This means that the
spatial segment is always aligned with the reference point so that
continuous identification of reference points can be dispensed with
or limited to a verification.
The reference points can be distinguished from the background on
the basis of their reflectivity, so that the position thereof can
be determined simply from the variation in the intensity of the
reflected radiation. By linking emission direction and intensity
maximum, it is possible to derive both distance and the direction
to the reference point as position information.
Advantageously, however, image recording and image processing
methods can also be used. In this case, linked with the distances,
images are additionally recorded by the positioning device. These
may consist of complete images of a visual area detected or, for
example, of partial images or sections in which the reference
points are localised, and the position information is derived from
the position in the image. With CCD and CMOS cameras a large number
of suitable sensors which can also be supplemented by suitable
optical components and can be integrated in the form of a
wide-angle endoscope also in miniaturised form in devices is
available for recording of images. The measured distances are
coordinated with the position information which consists, for
example, of angles which can be derived on the basis of the number
of pixels present between two identified reference points.
From the distances or the distances associated with the respective
angles, it is now possible to obtain the actual spatial position
and, with a knowledge of the emission axis of the radiation
relative to a reference axis of the measuring appliance, also the
orientation. For deriving this information, generally known methods
of photogrammetry and of image processing can be used. The
association of image and distance information has a large number of
advantages over the sequential surveying of individual points.
Because of the detection simultaneously or within a short time and
arrangement of the image measurements in the form of images,
coordination problems are avoided. Moreover, the detection of the
spatial arrangement or sequence of the measurements provides
additional information which can be used for the subsequent
determination of the actual position or actual orientation.
In comparison with known methods which determine a position in the
plane, mathematically more complex descriptions arise in the case
of three-dimensional problems.
In two dimensions, a rotational position is described by a single
angle, and the corresponding rotation group SO(2) is commutative
and isomorphous with the unit circle S.sup.1 (with complex
multiplication as a group operation).
In three dimensions, on the other hand, rotational position is
described by a point in the three-dimensional Lie group SO(3) which
is non-commutative and has, as 3-dimensional manifold, a
substantially more complicated topology, in particular is not
homeomorphic with the 3-dimensional unit sphere S.sup.3.
The identification of the reference points and hence the linkage of
the position information recorded by the positioning device with
the position of a specific reference point can be effected in
various ways. Firstly, the elements defining a reference point can
be made distinguishable so that a detected reference point can be
uniquely identified without further reference to other reference
points. For this purpose, it is possible to attach a code which,
for example, like a barcode, can be detected and evaluated in the
recorded image, or to specially design the physical properties of
an element. An example of such a design of the physical properties
is the superposition of a diffractive structure on a reflective
sphere. However, this can also be uniquely designed in its spectral
reflectivity. If an element designed in such a manner is detected
by a laser beam with two wavelengths, identification of the element
can be effected on the basis of the typical intensity relationship
of the reflection.
In addition, however, it is precisely image processing methods that
offer the possibility of using elements without designing them
individually, by also taking into account the arrangement of the
elements relative to one another. Since the spatial position of all
reference points is known, the position of the reference points
relative to one another, which is derived from a detected image,
can be used for permitting identification of the individual points.
For this purpose, it is advantageous if a coordination with
positions can be effected unambiguously from only a few reference
points and their position relative to one another. For ensuring
good identifiability, even in the case of only small detected
partial quantities, the reference points can be stochastically
distributed or be placed in the form of special arrangements, such
as, for example, a mathematical M-sequence.
If further components for position determination are used in the
measuring appliance, such as, for example, inertial sensors which
register a change relative to a known start position, this
information too can be used, optionally together with a direction
or inclination measurement, for identification of the reference
points detected in the spatial segment.
If only a small number of reference points is used or if it is
possible or expedient to establish or mount them only in a limited
region, a coarse search for automatic detection of reference points
can be used, which search proposes an alignment of the measuring
appliance to the user or aligns a component of the measuring
appliance which is suitable for the detection of the spatial
segment, so that no interaction with the user is required.
In order to be able to carry out an alignment or orientation
determination in addition to the location or position determination
of the measuring appliance, a link must be made between the
measurement of the reference points and distinguished axes of the
appliance. In this respect, directions to the reference points in
the form of vectorial quantities are also required in addition to
the measured distances. Said vectorial quantities can be derived,
for example, from the inclination measurements used for the
position determination.
Alternatively or in addition, however, the position of the
components of a scanner system can also be measured so that, in the
detection and surveying of a reference point, the direction of the
measuring beam relative to the axis of the appliance is also known.
The quantities required for this purpose can be reduced to a single
parameter. If, for example, the scanning movement is known, it can
be configured as a function of time so that the emission or
receiving direction then current can be concluded from the time of
a measurement. The determination of the spatial position as a
position and orientation measurement therefore in principle
requires only the measurement of a further, appliance-internal
quantity.
A measuring appliance according to the invention will generally
have further measuring functionalities which permit a use as a
geodetic instrument or are integrated in such an appliance. For
example, such a hand-held measuring appliance can be designed so as
to be capable of being used for surveying in the construction
sector, by integrating a further laser telemeter or providing the
distance measuring functionality which is in any case already
present according to the invention for further measurements. By
means of such an embodiment, it is possible to measure distances in
buildings without having to effect a separate position
determination and position storage in the case of each measurement.
The measured direction-related distances are automatically
coordinated as vectorial quantities with the position assumed in
the measurement and are stored or transmitted. In addition, further
measurements can also be carried out simultaneously.
Such an embodiment can also be used for carrying out the initial
establishment and surveying of the reference points. For this
purpose, reference points are established at positions which can be
seen at least from partial areas of the region to be used or
surveyed and can be made detectable by suitable elements. Below,
the positions of the reference points are surveyed from a known
initial position by recording angle and distance. If no angle
measuring functionality is available, a pure distance measurement
from a plurality of known initial positions can also be used
instead for deriving the positions of the reference points.
A further use according to the invention consists in the
combination with a positioning and/orientation measuring system
operating in a different manner. This further system may now have a
supporting function or may itself be supported. Thus, inertial
sensors which measure, for example, types of rotation and linear
accelerations frequently have drifts which lead to the deviation of
the measured actual position from the true position. A positioning
system according to the invention offers a suitable correction
functionality which corrects deviations at certain time intervals
by actual position determinations according to the invention. On
the other hand, the periods between the steps carried out according
to the invention can be supported by position determination by
means of inertial sensors. Furthermore, temporary loss of the
detection of reference points can be bridged by a further
positioning system so that either the number of reference points
can be reduced and/or the region accessible to measurements can be
briefly extended. Such a positioning device designed in hybrid form
can thus also compensate for the brief loss of a visual link to
reference points, so that the region of use is generally increased
in size and the device can be made more robust with regard to its
use. The same considerations apply in an analogous manner to
orientation measuring systems.
On the basis of the dimensions of geodetic instruments as well as
the components thereof and a small beam cross-section, highly
accurate and stable positioning is a critical requirement.
Advantageously, all components of the radiation source, beam
guidance and the controlling and evaluating components can
therefore be mounted on a common base plate or realised on a common
substrate. An optical structural element or structural part which
is particularly suitable with regard to the mounting requirements
and the necessary accuracy of mounting and is in the form of
components, and a total system, are described in DE 195 33 426 A1
and EP 1 127 287 B1. WO 99/26754 and European Patent Application
no. 02026648 not yet published on the date of filing describe
suitable methods for fixing miniaturized structural parts by means
of solder on a base plate. A suitable method for fixing a
miniaturised structural part on a support plate, in particular for
fine adjustment of optical components, is described, for example,
in European Patent Application no. 02026650 not yet published on
the date of filing.
In this context, the term "positioning device", "orientation
measuring device" or "hand-held measuring appliance" is always to
be understood as meaning generally a measuring instrument or an
instrument which is used in association with geodetic measurements
or machine guidance, such as, for example, a plumbing staff or a
location or direction determination of a construction machine. In
general, the invention relates to methods and apparatuses for
position and/or orientation determination for measurement or
checking of data having a spatial reference. In particular, a
geodetic instrument is to be understood here as meaning hand-held
telemeters and theodolites and also so-called total stations as
tacheometers with electronic angle measurement and electrooptical
telemeters. Equally, the invention is suitable for use in
specialised apparatuses having a similar functionality, for example
in military aiming circles or in the monitoring of industrial
structures or processes or machine positioning or guidance.
The method according to the invention and a hand-held measuring
appliance according to the invention or a local positioning and
orientation system according to the invention are described in more
detail below purely by way of example with reference to working
examples shown schematically in the drawing. Specifically
FIG. 1 shows the diagram of a possible embodiment of the first step
of the method according to the invention for positioning a
construction machine;
FIG. 2 shows the diagram of a possible embodiment of the second and
third steps of the method according to the invention for
positioning a construction machine;
FIG. 3 shows the initial situation for using the method according
to the invention in an interior room of a building;
FIG. 4 shows the diagram of a possible embodiment of the second and
third steps of the method according to the invention for position
determination in an interior room of a building with detection of
only one spatial segment;
FIG. 5 shows the diagram of an example of the scanning movement in
the automatic detection and derivation of position information for
a first and a second reference point;
FIG. 6a-b show the diagram of suitable scanning movements for a
method according to the invention;
FIG. 7a-b show the diagram of a further possible embodiment of the
second and third steps of the method according to the invention for
position determination in an interior room of a building with
detection of two spatial segments independently of one another;
FIG. 8 shows the diagram of the mathematical conditions for
deriving the actual position and actual orientation of the moveable
measuring appliance from the position information and the positions
of the first and second reference points;
FIG. 9 shows the diagram of the use of a method according to the
invention in combination with a further positioning or orientation
measuring device;
FIG. 10a-b show the diagram of a first and second possible
embodiment of a measuring appliance according to the invention;
FIG. 11 shows the diagram of components of the first embodiment of
a measuring appliance according to the invention;
FIG. 12 shows the diagram of the use, according to the invention,
of a method according to the invention with a third embodiment of a
measuring appliance according to the invention for establishing
processing positions, and
FIG. 13 shows the diagram of fundamental mathematical relationships
for deriving the spatial position of the moveable measuring
appliance.
FIG. 1 shows, by way of example, the first step of a method
according to the invention for positioning a construction machine.
By means of a total station 1 as a geodetic surveying instrument,
reference points 2a mounted on adjacent buildings on a building
site are surveyed and their spatial position is determined. This
establishment of the reference points 2a at elevated positions
permits good viewability and detectability from large parts of the
building site. The location of the total station 1 is known as the
initial position of the method. In principle, the position
determination of the reference points 2a can, however, also be
effected using other apparatuses or methods. In particular, the
position determination of the reference points can also be effected
according to the invention by means of a positioning device
according to the invention which is present at a known initial
position. If points whose position is in any case known exist,
these can also be made detectable as reference points and used in
the method according to the invention.
FIG. 2 shows, by way of example and purely schematically, the
second and third steps of a method according to the invention for
positioning the construction machine 3. A positioning device 4a
which detects a spatial segment 5 in which, in the general case of
an angle and distance measurement, at least two reference points
2a' should be present is mounted on the construction machine 3. If
this spatial segment 5 comprises less than two reference points
2a', it may be necessary to change the size or orientation of the
detected spatial segment 5. For a local positioning system based
purely on distance measurements, however, at least three reference
points 2a' present in the spatial segment 5 must be detected and
their distance to the positioning device 4a must be measured. The
actual position is derived from the measured values.
The initial situation for another field of use of the method
according to the invention is shown in FIG. 3 by way of example for
a use in an interior room of a building. Reference points 2b are
mounted on the walls of the room before the beginning of a
surveying job and are surveyed with respect to their position. This
can be effected, for example, using a hand-held telemeter as a
measuring appliance with inclinometer and direction meter. By means
of this telemeter, the positions of the reference points 2b are
derived in succession from a known initial position by measurement
of angle of inclination, direction and distance.
FIG. 4 shows the diagram of the subsequent steps of the method
according to the invention for position determination in an
interior room of a building. A measuring appliance 4b according to
the invention detects a spatial segment 5' in which at least two
reference points 2b' are detected. The two reference points 2b'
detected and scanned in the spatial segment 5' are surveyed with
respect to their distances and angles of inclination by the
measuring appliance 4b. However, alternative amounts of variables
can also be used for determining the actual position and/or actual
orientation, such as, for example, the approach which is shown in
FIG. 2 and based purely on distance measurements but for which at
least three reference points would have to be surveyed with respect
to their distance. The actual position of the positioning device 4b
can be concluded from the distances and angles of inclination as
location information, taking into account the absolute positions of
the reference points 2b'. As is also the case below, the diagram is
purely schematic so that the size relationships of the objects
shown are not to be regarded as being to scale.
FIG. 5 shows the diagram of an exemplary scanning movement in the
automatic detection and derivation of location information. The
spatial segment 5' is detected as substantially as possible by
means of a laser beam in a scanning movement 6. For scanning
relatively large spatial segments, as a rule a movement about two
axes is effected. In this example, the laser beam is guided with a
conical detection region in a rosette-like scanning movement 6 over
the spatial segment 5' with circular cross-section, the position of
the device components used for the scanning movement 6 being
detected. When the laser beam strikes one of the reference points
2b' present in the spatial segment 5', a reflection of high
intensity is generated and is used for detecting the reference
point 2b', for example by using a filter or detection of
reflections which is dependent on a threshold value. By means of
the laser beam, a measurement of the distance to the reference
point 2b' is effected simultaneously. If the scanning movement 6
takes place rapidly compared with a movement of the spatial segment
5' the position of the reference points 2b' relative to one another
can be concluded from the position of the received reflections as a
function of time, since the parameters of the scanning movement 6
and its course as a function of time are known.
FIG. 6a-b show the diagram of suitable scanning movements for a
method according to the invention. FIG. 6a shows a further
rosette-like scanning movement 6' with lower degree of coverage of
a completely detected circular spatial segment. However, other
forms of scanning movement 6'' can also be used according to the
invention. For example, a rectangular spatial segment which
corresponds, for example, to a matrix of pixels 7 can be filled by
a zig zag scanning movement 6''. If the scanning movement is known,
it can also be configured, for example with the time or a position
of the shaft of a common drive motor which drives all part
movements of the scanning process together as a parameter.
FIG. 7a-b show an exemplary use of two spatial segments 5'' in the
automatic detection and derivation of location information.
In a second embodiment, the measuring appliance 4c has two trackers
which are each formed for tracking reference points 2b. Each of the
two trackers searches, independently of the other, for a spatial
segment 5'' in which a detectable reference point 2b' is present.
After the detection of the reference point 2b', the latter is
continuously tracked and the spatial segment 5'' thus remains
continuously aligned with the respective coordinated reference
point 2b'. In spite of the different positions of the measuring
appliance 4c which are shown in FIG. 7a and FIG. 7b, the detection
of the same reference points 2b' is always effected so that a
change and a fresh identification of reference points are not
necessary.
FIG. 8 illustrates the mathematical conditions for a possibility
for deriving the actual position AP of the moveable measuring
appliance from the location information and the positions of the
first and second reference points 2b'. From the positioning device
present at the actual position AP, the first distance A together
with the associated angle .alpha. of inclination and the second
distance B together with the associated angle .beta. of inclination
to both reference points 2b' are measured. From a knowledge of
these quantities, the actual position AP can be unambiguously
derived--apart from reflection at a vertical plane through the two
reference points 2b'. Alternatively, instead of the measurement of
the second distance B, it is also possible to measure the angle
.gamma. between the two reference points or to derive said angle
from a recorded image. From these quantities, too the actual
position can be unambiguously derived--likewise apart from the
reflection. If moreover the angle relative to an axis of the
appliance is known, the orientation of the measuring appliance can
also be determined.
FIG. 9 schematically shows the use of a method according to the
invention in combination with a further positioning or orientation
measuring device. Starting from a first position from which a
measurement to reference points has taken place, the measuring
appliance is moved along a trajectory T, the measuring appliance
being equipped with inertial sensors as a further positioning or
orientation measuring device, which sensors continuously carry out
a position or alignment determination. Owing to drift effects, an
apparent position or alignment along the first interpolation path
IP1 is indicated thereby, the development of which is corrected
again after a time interval by a determination of a first actual
position AP1 or of an actual orientation by means of the method
according to the invention. During passage through the trajectory,
the development of the apparent positions along the second
interpolation path IP2 and the third interpolation path IP3 are
corrected at time intervals in succession by the second actual
position AP2 and third actual position AP3 measured by the method
according to the invention or the actual orientations. By the
combination of the two methods, either positions present between
the measurements of the method according to the invention can be
derived, regions not provided with reference points can be overcome
or a correction of the device based on inertial sensors can be
effected. In addition, an extension of the field of use and
facilitation of the handling are realised by such a
combination.
FIG. 10a-b graphically show two possible embodiments of the
measuring appliance according to the invention.
The measuring appliance 4b shown in FIG. 10a as a first embodiment
has a housing 8 on the top of which keys 10 for inputting data and
control commands are mounted. In a display field 11, results of
measurements are displayed. The emission of laser radiation and the
detection of the spatial segment are effected through a hood 9
which is present on the measuring appliance 4b and is transparent
to radiation. Because of the curvature of the hood 9, solid angle
regions located to the sides of the measuring appliance 4b can also
be detected.
FIG. 10b shows a second embodiment of the measuring appliance 4c.
In addition to housing 8, keys 10 for inputting data and control
commands and a display field 11, the measuring appliance 4c has two
hoods 9' which are transparent to radiation and through which the
emission of laser radiation and the detection of a spatial segment
in each case take place. The emission and detection are controlled
by trackers which permit automated target tracking of reference
points.
FIG. 11 shows the diagram of components of the first embodiment of
a measuring appliance 4b according to the invention, comprising a
housing 8 and the components integrated therein. Keys 10 and a
display field 11 for inputting and outputting data and control
instructions are present on the housing 8. Laser radiation L which
is guided by means of deflection elements 13 onto a rotatable pair
14 of prisms as a control component is emitted by a first radiation
source 12. By means of the rotatable pair 14 of prisms, the angle
at which the laser radiation L strikes a mirror 15 is periodically
varied so that a rosette-like scanning movement of the laser beam L
emitted by the measuring appliance 4b through the hood 9 results.
The position of the components used for the emission can be
continuously detected for deriving the actual orientation. The
laser radiation reflected back by a target, in particular a
reference point, is fed back via the same beam path to the
radiation source 12, in which in this case a receiver for distance
measurement is structurally integrated.
The radiation reflected back by a reference point present within
the detection region EB is moreover guided via an optical system in
the form of endoscope 16 to a camera 17 as an image-recording
component. By means of the camera 17, detection of the reference
points and identification thereof by image processing methods are
permitted simultaneously with the distance measurement. In
particular, an angle measurement can be carried out here by
counting the pixels present between two reference points.
For control and data processing, the measuring appliance 4b
according to the invention has a computing unit 20 comprising a
measuring component for automatic detection of reference points
which have been made detectable and for derivation of location
information of the reference points and of a position component for
deriving the actual position and actual orientation of the
measuring appliance 4b from the location information of the
reference points.
Optionally, the measuring appliance may also have inertial sensors
21.
In order to provide simultaneous functionality as a geodetic
instrument, the measuring appliance 4b may have a second radiation
source 18 which is likewise in the form of a telemeter and by means
of which distance measurements to targets to be recorded are
possible. By combining measuring appliance 4b and a conventional
telemeter, it is possible to establish an automatic link between
distance information and actual position or actual orientation and
thus to simplify and accelerate the entire surveying process.
Of course, these figures which are shown are only examples of
possible embodiments of apparatuses and methods. Thus, the
components used in FIG. 10 could also be used according to the
invention in other configurations and sequences. In addition, it is
within the ability of the person skilled in the art to use
additional or alternative optical components, for example having a
diffractive effect, and components which have the same or a similar
effect or functionality and are generally used in laser physics or
laser technology. In FIG. 10, necessary electronic control,
position measuring and supply parts and mounting components are not
shown merely for reasons of clarity.
FIG. 12 explains the use, according to the invention, of the method
according to the invention for establishing processing positions
BP. With a third embodiment of the measuring appliance 4d according
to the invention as a positioning device, in each case a start
position SP and an end position EP are established on a workpiece
to be processed, which is represented here by way of example by a
block board 22. Examples of the processing of workpieces are the
hammering of nails into walls or the drilling of holes. By means of
a strip 23 mounted to the side of the measuring appliance 4d and
having a marking opening, the processing positions BP reached can
be marked on the block board 22. Thus, a departure of marking
opening and reference point of the position determination from one
another in the measuring appliance 4d can be taken into account by
calculation. The distance defined by start position SP and end
position EP is divided into predetermined sections by a computing
component in the measuring appliance 4d. These sections may be both
equidistant and determined according to a more complex pattern. The
measuring appliance 4d is subsequently guided over the blackboard
22, a display indicating in each case the reaching of one of the
predetermined processing positions BP. This can then be marked for
further processing steps. For such an application, the measuring
appliance 4d can be equipped with rollers or sliding segments,
similarly to a computer mouse.
FIG. 13 illustrates fundamental mathematical relationships for
deriving the spatial position of the moveable measuring
appliance.
For measurement of the position in a position determination, in
principle three minimum variants are possible with regard to the
choice of measured values to be recorded.
1. Measurement of the distances to two reference points and
measurement of the elevation of one of the reference points.
2. Measurement of distance and elevation to one of the two
reference points and measurement of the angle between the two
reference points.
In both cases, the two reference points are not permitted to be
vertically one above the other and in both cases there are in a
favourable case two solutions for the position, namely symmetrical
to the plane which contains the two reference points and is
perpendicular to the horizontal plane.
This ambiguity can be eliminated in practice in various ways, for
example by means of a direction meter, for example a compass, there
being no need to set any high accuracy requirements for said
compass, or by means of a priori knowledge of the setup. Thus, for
example, the reference points are on a wall and the object cannot
measure through the wall or, at the start, it is known on which
side of the symmetry plane the object is present and it is then
tracked and can thus also pass through the symmetry plane.
The points with constant distance and elevation to a reference
point thus lie on a circle of latitude of the sphere with the
reference point as centre and the distance as radius.
3. Measurement of the elevations of both reference points and
measurement of the distance to one of the reference points.
Here too the two reference points are not permitted to be
vertically one on top of the other and in addition the reference
point to which the distance is measured is not permitted to lie at
the same (vertical) height as the object, since otherwise the
elevation of the reference point to which the distance was not
measured is zero for all points of the circle of latitude. In a
favourable case, there are once again two symmetrical solutions for
the position.
In order to obtain an accuracy sufficient for geodetic
applications, it may be advantageous to measure distance and
elevation to both reference points. There is a higher accuracy for
this approach, owing to the redundancy. A measurement of distance
and elevation to one of the two reference points and measurement of
the angle between the two reference points does however have
greater hardware complexity owing to the necessary measurement of
the intermediate angle.
Below, it is explained how a three-dimensional position d can be
derived in the minimum case of a determination of only two
distances .rho..sub.1, .rho..sub.2 to two reference points
(position vectors x.sub.1, x.sub.2) and the elevation .alpha..sub.1
to the first reference point. A triangle defined by the vectors d,
x.sub.1, x.sub.2 serves as a starting point for the consideration
of the general three-dimensional case of a position determination,
FIG. 13 showing the figure lying in the plane of this triangle.
The height h>0 of the triangle and the signed height section y
are calculated using planar geometry according to
.rho..rho..times..rho. ##EQU00001##
In FIG. 13, y is <0; in a case in which the height is within the
triangle, y is >0.
All positions d which are still suitable after use of the measured
distances now lie on the circle in the plane perpendicular to
x.sub.2-x.sub.1, with the centre being the base of the vertical and
radius h. In order to describe this circle analytically in a simple
manner, the following orthonormal trihedron adapted to the
situation is introduced:
.times..times..times. ##EQU00002## Here, x designates the vector
product and e.sub.3 is the vertical base vector of the geodetic
coordinate system. The vector .sub.2 is therefore horizontal. The
position vectors d on said circle which are still suitable can
therefore be described as follows: d=x.sub.1+y .sub.1+h( .sub.2 cos
.phi.+ .sub.3 sin .phi.) (3) the angle .PHI. being a still unknown
parameter. It must be determined by the measured elevation
.alpha..sub.1. The following is true .rho..sub.1 sin
.alpha..sub.1=e.sub.3.sup.T(x.sub.1-d)=x.sub.1.sup.3-d.sup.3 (4)
the third component of the vectors being written with the
superscript 3. Together with equation (3), the following condition
arises .rho..sub.1 sin .alpha..sub.1=-y .sub.1.sup.3-h(
.sub.2.sup.3 cos .phi.+ .sub.3.sup.3 sin .phi.) (5) which generally
permits two solutions for .PHI.. The solutions to equation (5) can,
for example, be determined numerically. If they are substituted
into (3), the two possible positions follow. Equation (5) can also
be solved explicitly: it has the form A cos .phi.+B sin .phi.+C=0
(6) where A=h .sub.2.sup.3, B=h .sub.3.sup.3,
C=ye.sub.1.sup.3+.rho..sub.1 sin .alpha..sub.1 (7) If c=cos .phi.,
s=sin .phi. (8) it is true that Ac+Bs+C=0, c.sup.2+s.sup.2=1.
The solution to this system of equations gives
.ident..times..times..phi..+-..times..times..ident..times..times..phi..-+-
..times. ##EQU00003##
Substitution in c.sup.2+s.sup.2=1 shows that only either the two
upper or the two lower choices of the sign are permissible in (9),
and two solutions therefore follow.
Thus, the equations (1), (2), (7), (9) and (3) are used, i.e. in
succession, for the explicit calculation of the position vector
d.
For the parallel determination of location and alignment, 6 degrees
of freedom have to be determined. In the equations below, vector
components are written as superscripts, where
##EQU00004## represents the direction vector to the i th reference
point and the projection of e.sub.3 onto the plane defined by
.sub.1 and .sub.2, measured by an inclination sensor, being
designated according to .eta..sup.1:= .sub.1.sup.Te.sub.3,
.eta..sup.2:=
.sub.2.sup.Te.sub.3((.eta..sup.1).sup.2+(.eta..sup.2).sup.2.ltoreq.1)
Here, {e.sub.1,e.sub.2,e.sub.3} is a fixed orthonormal trihedron
and {e.sub.1,e.sub.2,e.sub.3} is an orthonormal trihedron fixed
relative to the object. The following relationships are furthermore
applicable:
.rho..times..rho..times..times..rho..times..times..times..times.
##EQU00005## .di-elect cons..times..di-elect cons.
##EQU00005.2##
If inclinations are measured by means of an inclination sensor, for
example, position d.epsilon.R.sup.3 and rotational position
E.epsilon.SO(3) can be calculated by means of the equations
.times..rho..times..rho..times..times..times..times..times..perp..functio-
n..function..times..eta..times..times..eta..times..times..eta..times..di-e-
lect cons..times..rho..times..times..times..function. ##EQU00006##
here, I is the index quantity and |I| is the number of reference
points used for the measurement.
Instead of the equation (11), it is also possible to use the
following equations:
.times..eta..function..times..times..eta..times..eta..times..function..ti-
mes..times..eta..times. ##EQU00007##
.times..eta..function..times..times..eta..times..eta..times..function..ti-
mes..times..eta..times. ##EQU00007.2##
.times..eta..function..times..times..eta..times..eta..times..function..ti-
mes..times..eta..times. ##EQU00007.3##
If a determination is carried out without using an inclination
sensor, the following equations can be used:
.times..rho..times..rho..times..times..times..times..ltoreq.<.ltoreq.
##EQU00008##
.times..times..times..function..times..times..times..function..times..tim-
es..times..times..times..times. ##EQU00008.2## .times..di-elect
cons..times..rho..times..times..times..function. ##EQU00008.3##
In the figures the steps of the method, buildings and instruments
used are shown purely schematically. In particular, no size
relationships or details of the image processing or surveying of
the reference points are evident from the diagrams. The points
shown only by way of example as reference points also represent
more complex structures or the elements which make a point
detectable.
* * * * *